Supporting mpio for logical volume backed virtual disks

ABSTRACT

Embodiments include systems, methods, and computer program products to perform an operation for enabling multipath I/O for logical volume backed virtual disks through redundant virtual I/O servers (VIOSs) on a computing system. The operation generally includes creating, from a physical storage device, a logical volume on a first VIOS. The logical volume on the first VIOS is activated in a first access mode. The operation also includes importing the logical volume to a second VIOS. The logical volume on the second VIOS is activated in a second access mode different from the first access mode. The operation further includes mapping the logical volume on the first and second VIOSs as a backing storage device for at least one logical partition hosted on the computing system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 15/416,885, filed Jan. 26, 2017. The aforementioned relatedpatent application is herein incorporated by reference in its entirety.

BACKGROUND

The present disclosure generally relates to techniques for storagevirtualization, and more specifically, to techniques for supportingmultipath input/output (I/O) (MPIO) for logical volume backed storagedevices through redundant virtual I/O servers (VIOSs) on a clientdevice.

In many cloud and virtualized environments, it is becoming increasinglyimportant to provide near-continuous availability of resources in theenvironment. For example, as cloud environments move toward using lowcost commodity hardware to support cloud infrastructures, providing highavailability can reduce chances of an outage due to maintenance,hardware failures, etc. To provide high availability and redundancy,administrators often logically partition the resources of computingsystems through virtualization. These resources can include processors,memory, I/O devices, storage, etc.

On a computing system, a firmware layer (e.g., a hypervisor) is used toexpose virtualized computing hardware to different logical partitions(or virtual machines). Each logical partition can run a differentoperating system (OS). The hypervisor can provide each OS with a set ofvirtualized computing hardware. Referring in particular to I/O, acomputing system may be provided with a special logical partition forI/O virtualization, referred to herein as a virtual I/O server (VIOS). AVIOS is generally configured to provide virtual I/O resources to thelogical partitions of a computing system and enable shared access (bythe logical partitions) to physical storage resources, e.g., disks,tape, optical media, etc. In some cases, a computing system can includemultiple VIOSs to provide redundancy and multiple paths to the physicalstorage resources.

Storage virtualization, in general, can be implemented in different wayson different hypervisors. One example storage virtualization techniqueis virtual Small Computer Serial Interface (SCSI) based on aclient-server relationship. With virtual SCSI, client logical partitionscan share disk storage, tape, optical devices, etc., that are assignedto the VIOS logical partition. The VIOS owns the physical storage andacts as a storage server (or SCSI target device). The client logicalpartitions access the virtual SCSI backed physical storage devicesprovided by the VIOS as clients (or SCSI initiators). Examples of thebacking storage devices include disks, logical volumes, files, etc.

SUMMARY

One embodiment presented herein includes a method for enabling MPIO forlogical volume backed virtual disks through redundant VIOSs on acomputing system. The method generally includes generally includescreating, from a physical storage device, a logical volume on a firstVIOS. The logical volume on the first VIOS is activated in a firstaccess mode. The method also includes importing the logical volume to asecond VIOS. The logical volume on the second VIOS is activated in asecond access mode different from the first access mode. The methodfurther includes mapping the logical volume on the first and secondVIOSs as a backing storage device for at least one logical partitionhosted on the computing system.

Other embodiments include, without limitation, a computer programproduct that includes a storage medium having computer-readable programcode that enables a processing unit to implement one or more aspects ofthe disclosed methods as well as a system having a processor, memory,and application programs configured to implement one or more of thedisclosed methods.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates an example computing environment configured tovirtualize a logical volume from multiple VIOSs on a client computingsystem, according to one embodiment.

FIG. 2 illustrates an example configuration of a computing systemconfigured to enable MPIO for logical volume backed storage devicesthrough redundant VIOSs, according to one embodiment.

FIG. 3 illustrates an example of a computing system configured to switchone of multiple paths for accessing a logical volume during pathfailover, according to one embodiment.

FIG. 4 is a flow chart illustrating a method for configuring a client toaccess a logical volume from multiple VIOSs on a computing system,according to one embodiment.

FIG. 5 is a flow chart illustrating a method for identifying andcreating multipath paths to a logical volume backed device via multipleVIOSs on a computing system, according to one embodiment.

FIG. 6 is a flow chart illustrating a method for switching one ofmultiple paths used to access a logical volume, according to oneembodiment.

FIG. 7 is a block diagram illustrating a computing system configured toprovide support for MPIO for logical volume backed storage devicesthrough redundant VIOSs on the computing system, according to oneembodiment.

DETAILED DESCRIPTION

In many cases, logical volumes (i.e., a portion of a physical storagedrive (or drives) exposed as an independent device) can be employed asbacking storage devices for virtualized storage devices for clients.Administrators, for example, can use a logical volume backing devicethat spans across multiple physical disks to achieve a larger backingstorage device. In another example, administrators can use a logicalvolume backing device that partitions one or more physical disks toachieve a smaller backing storage device. In addition, logical volumebacking devices can grow and shrink dynamically. However, while logicalvolumes can be used as backing devices, it is typically not possible(e.g., with current techniques) to enable multipath I/O (MPIO) throughredundant VIOSs with logical volumes as backing devices, becausesimultaneously accessing a logical volume as a virtual disk frommultiple client partitions can cause inconsistency of the logicalvolume.

Embodiments presented herein provide techniques for virtualizing alogical volume from multiple virtual I/O servers (VIOSs) and providingmultiple access routes through the VIOSs to the logical volume.

For example, a multipath component on a client computing system can beconfigured to create a volume group over a shared storage area network(SAN). The volume group, for example, may span over one or more physicaldisks. Once created, the multipath component can create one or morelogical volumes on the volume group and import the logical volumes tomultiple VIOSs on the same client computing system. The logical volumescan be used as backing storage devices for clients (e.g., virtualmachine(s), logical partition(s), etc.) hosted on the client computingsystem. That is, the logical volumes can be used to back a virtualstorage device (e.g., such as a virtual disk) on one or more clients.Further, as described below, the multipath component can be configuredto identify (for a client) the same logical volume as a virtual disk(e.g., virtual small computer serial interface (SCSI) disk) via themultiple VIOSs and create multiple paths to the logical volume.

For example, assuming a client computing system is configured with twoVIOSs, the multipath component can configure the path from the firstVIOS to the logical volume as the active path and the path from thesecond VIOS to the logical volume as the inactive (or passive) path. Theactive path may be used for I/O operations (e.g., read/write access) andthe inactive path may be used as a standby path (e.g., read onlyaccess). In this manner, the multipath component can enable MPIO tological volume backed storage devices through multiple redundant VIOSson a client computing system while preventing simultaneous access to thelogical volume from the VIOSs.

Additionally, the multipath component can be configured to switch to oneor more of the redundant passive paths in the event the active pathfails. Continuing with the above example of two VIOSs, once themultipath component determines the active path (via the first VIOS) hasfailed, the multipath component can send a command (e.g., SCSI modeselect command) to the first VIOS to switch the active path to a passivepath, and send another command to the second VIOS to switch the inactivepath to an active path. The client may then start accessing (e.g.,performing read/write I/O operations) the logical volume via the activepath from the second VIOS.

Note that many of the following embodiments refer to a computing systemwith two VIOSs as a reference example of a computing system withmultiple redundant VIOSs that can be configured to provide MPIO forlogical volume backed virtual disks. Those of ordinary skill in the artwill recognize that the techniques presented herein can be applied to acomputing system with any number of VIOSs.

FIG. 1 illustrates an example computing environment 100 configured toenable support for MPIO for logical volume backed storage devicesthrough redundant VIOSs, according to one embodiment. As shown, thecomputing environment 100 includes a computing system 110 connected vianetwork 150 to computing system 160. In general, the network 150 may bea wide area network (WAN), local area network (LAN), wireless LAN(WLAN), etc. In one embodiment, the network 150 is Ethernet. Each of thecomputing systems 110 and 160 can be any kind of physical computingsystem having a network interface, such as a desktop computer, laptopcomputer, mobile device, tablet computer, server computing system, andthe like. The computing system 110 is also connected via the storagearea network (SAN) 140 to one or more physical storage 142A-M. Examplesof physical storage 142A-M include physical disks, external LUNS, tapedrives, optical storage devices, tape storage devices, and the like.

The computing system 110 includes one or more logical partitions (LPARs)120, a hypervisor 126, and one or more VIOS partitions 128. Thecomputing system 110 may spawn, using the hypervisor 126, a number ofLPARS 120 that can belong to a number of independent entities (e.g.,enterprises, organizations, individual users, etc.). The hypervisor 126is software and/or hardware that manages and executes the LPARs 120(also referred to as virtual machines or VMs) in the computing system110. The hypervisor 126 is generally an intermediary between the LPARs120 and the hardware in the computing system 110. For example, thehypervisor 126 can manage physical resource allocation and accessphysical resources (e.g., such as processors, I/O, memory, etc.) onbehalf of a given LPAR 120.

The LPAR 120 includes a multipath component 122, one or more virtualstorage devices (e.g., virtual disk(s) 134), and virtual clientadapter(s) 124. Each LPAR 120 hosted in the computing system 110 can runan independent operating system in order to execute one or moreapplications (or processes). Examples of operating systems includeversions of the UNIX operating system (such as the AIX operatingsystem), distributions of the Linux operating system, etc. (UNIX is aregistered trademark of The Open Group in the United States and othercountries, or both. Linux is a registered trademark of Linus Torvalds inthe United States, other countries, or both). More generally, anyoperating system supporting the functions disclosed herein may be used.

The VIOS 128 is a partition that is generally configured to providevirtualized storage and/or network adapters to LPARs 120 in thecomputing system 110. For example, the VIOS 128 can allocate virtual I/Oresources (e.g., virtual ports, virtual adapters, etc.) to LPARs 120that the LPARs 120 can use to access the physical storage resources(e.g., physical storage 142A-M). The VIOS 128 can also be configured tovirtualize the physical storage resources into one or more virtualizedstorage devices 134, such as virtual SCSI disk. The virtual storagedevices 134 can be backed by physical disks, external LUNs, logicalvolumes, etc. As shown, the VIOS 128 includes virtual server adapter(s)130 and physical adapter(s) 132. The VIOS 128 allows the LPAR 120 toconnect to physical resources, e.g., such as the physical adapter(s) 132and physical storage 142A-M on the SAN 140 via the virtual clientadapter(s) 124 and virtual server adapter(s) 130. In one embodiment, thevirtual client adapter(s) 124 includes virtual SCSI client adapters andthe virtual server adapter(s) 130 include virtual SCSI server adapters.In one embodiment, the VIOS 128 and/or the computing system 160 can beconfigured to map (for the LPARs 120) the interaction between thevirtual client adapters (e.g., on each LPAR 120) and the virtual serveradapters. Once mapped, the multipath component 122 can be configured toprovide a mapping between the virtual adapters and the physical storage.

The computing system 160 is generally configured to provide managementfunctions for the computing system 110. In one embodiment, the computingsystem 160 is an example of a management console that can be used toconfigure and/or manage the resources within the computing system 110.One example of a management console is the Hardware Management Console(HMC) by International Business Machines®. The computing system 160 canuse the management component 162 to configure and manage the physicaland/or virtual resources in the computing system 110, monitor theoperation of the resources, perform dynamic partitioning of theresources, activate and manage capacity on demand resources, assignaddresses to the resources, and the like. The management component 162can interact with the VIOS(s) 128, hypervisor 126 and/or LPAR(s) 120 tomanage the physical and/or virtual resources. In one embodiment, themanagement component 162 provides an interface (e.g., a graphical userinterface (GUI)) that allows a user (or administrator) to configureand/or manage resources within the computing system 110. In oneembodiment, an administrator can interact with the computing system 160remotely via the network 150 from another computing system (not shown).

As mentioned above, in cases where logical volumes are used to back thevirtualized storage devices (e.g., virtual SCSI disk), it may not bepossible to support MPIO through redundant VIOS for the logical volumebacked devices, as data inconsistency issues can arise when multipleVIOS have access (e.g., read/write access) to the same logical volume.

As such, embodiments presented herein provide techniques forvirtualizing a logical volume in order to enable MPIO through redundantVIOS while avoiding data inconsistency issues.

For example, the management component 162 within the computing system160 can be configured to create multiple VIOSs for clients (e.g., LPARs120) on the same computing system 110. The management component 162 canconfigure the mapping between the virtual I/O adapters in the LPARs 120and the virtual I/O adapters in the multiple VIOSs. Once configured, themultipath component 122 can create a concurrent volume group over ashared SAN disk for a first VIOS (e.g., VIOS 128A) on the computingsystem 110 and activate the volume group in read/write mode for thefirst VIOS. The volume group may include one or more physical volumes,each of which can include a hard disk, portion of a hard disk, logicalunit number (LUN), etc. For example, as shown in FIG. 2, the volumegroup 210 may include one or more disks 142A-M.

Once the volume group is created, the multipath component 122 can createlogical volumes on the volume group. Referring again to FIG. 2, themultipath component 122 can create logical volumes 220A-220N on volumegroup 210. In one embodiment, one or more of the logical volumes 220 canspan over multiple physical disks 142. In one embodiment, one or more ofthe logical volumes 220 can include a partition of a physical disk 142.The multipath component 122 can then import the volume group onto asecond VIOS (e.g., VIOS 128B) on the computing system 110 and activatethe volume group in read only mode for the second VIOS. The multipathcomponent 122 can map (via the first VIOS) the logical volume(s)associated with the volume group as backing storage devices for virtualdisk(s) 134 on the LPAR 120, and map (via the second VIOS) the samelogical volume(s) as backing storage devices for the virtual disk(s) 134on the LPAR 120.

Additionally, the multipath component 122 can enable the client (e.g.,LPAR 120) to identify the same logical volume backed device via themultiple VIOS and create multiple paths to the logical volume backeddevice. For example, in one embodiment, the multipath component 122 canbe configured to determine whether the same logical volume is being usedto back the virtual disk from multiple VIOSs based on a logical volumeidentifier (LVID) associated with the logical volume. The LVID isgenerally a unique identifier associated with each logical volumebacking device. As part of the device discovery protocol, the multipathcomponent 122 can be configured to send an inquiry command (e.g., SCSIinquiry command) to the first and second VIOSs on the computing system110. Each VIOS on the computing system 110 can be configured (e.g., bythe multipath component 122 and/or management component 162) to emulatea device specific SCSI mode page for the logical volume backed devicesthat the multipath component 122 can use to set and/or retrieveconfiguration settings of the logical volume backed devices.

In response to the inquiry command, each VIOS can embed the LVID of thelogical volume backing device in an inquiry response (e.g., SCSI inquiryresponse) and send the inquiry response to the multipath component 122.Once the multipath component 122 detects that the same LVID is receivedfrom both VIOS (e.g., the LVIDs match), the multipath component 122 cancreate multiple paths to the same logical volume backing device via thefirst and second VIOS (e.g., as part of its device discovery protocol).In one embodiment, to determine which of the paths is active/inactive,the multipath component 122 can send mode sense commands (e.g., SCSImode sense commands) to each VIOS. Continuing with the example describedabove, if the first VIOS is configured for read/write access to thelogical volume, the first VIOS can send a response indicating the pathfrom the first VIOS to the logical volume is an active path (e.g.,active path 230 in FIG. 2). Similarly, if the second VIOS is configuredfor read only access to the logical volume, the second VIOS can send aresponse indicating the path from the second VIOS to the logical volumeis a passive (inactive) path (e.g., passive path 232 in FIG. 2).

In some embodiments, the multipath component 122 can be configured toswitch paths in the event the multipath component 122 determines that anaccess operation to the logical volume via one of the paths fails.

FIG. 3 illustrates one example of a path failover scenario with logicalvolume backed virtual disks, according to one embodiment. As shown inFIG. 3, the multipath component 122 may initially create, for the LPAR120, two different paths for accessing the logical volume 220. Oncecreated, the LPAR 120 may use the active path via VIOS 128A forread/write I/O, and use the passive path via VIOS 128B for read onlyoperations.

As further shown in FIG. 3, in some cases, if an I/O (via the activepath) fails and all retries for the I/O fail, the multipath component122 can send a mode select command (e.g., SCSI mode select command) tothe first VIOS 128A via the active path to switch the active path topassive (e.g., read only mode). In some cases, if the first VIOS 128A isdown, the command may be rejected (e.g., by the hypervisor 126). In suchcases, the multipath component 122 may not have to switch the activepath to passive as the first VIOS 128A is not accessing the logicalvolume. In some cases, if the first VIOS 128A is active, after sendingthe mode select command, the multipath component may receive a returnmessage indicating that the first VIOS 128A has changed the permission(or configuration) of the volume group to read only. The multipathcomponent 122 may also send a mode select command to the second VIOS128B via the inactive path to switch the inactive path to active (e.g.,read/write mode). Once switched, the client may start I/O via the newactive path (e.g., via the second VIOS 128B). In this manner, themultipath component 122 can enable support for MPIO for logical volumebacked disks. Note that while FIGS. 2 and 3 illustrate the logicalvolume backed storage devices as separate from the VIOSs in thecomputing system, in some embodiments, the logical volume backed storagedevice may be within each redundant VIOS.

FIG. 4 is a flow chart illustrating a method 400 for configuring aclient to access a logical volume from multiple VIOSs on a computingsystem, according to one embodiment. As shown, the method begins atblock 402, where the multipath component 122 creates a concurrent volumegroup on a shared disk on a first VIOS (e.g., VIOS 128A) on a computingsystem (e.g., computing system 110). At block 404, the multipathcomponent 122 activates the volume group in read/write mode for thefirst VIOS. At block 406, the multipath component 122 creates a logicalvolume on the volume group. At block 408, the multipath component 122imports the volume group on a second VIOS (e.g., VIOS 128B) on thecomputing system. For example, in one embodiment, the importvg commandcan be used to import the volume group to the second VIOS. At block 410,the multipath component 122 activates the volume group in read only modefor the second VIOS. At block 412, the multipath component 122 maps thelogical volume on the first and second VIOSs as a backing storage devicefor the client (e.g., LPAR 120) on the computing system.

FIG. 5 is a flow chart illustrating a method 500 for creating multipathpaths to a logical volume backed device via multiple VIOSs on acomputing system, according to one embodiment. As shown, the methodbegins at block 502, where the multipath component 122 sends an inquirycommand to the first VIOS (e.g., VIOS 128A) and second VIOS (e.g., VIOS128B). At 504, the multipath component 122 receives a first inquiryresponse that includes a logical volume identifier from the first VIOS.The embedded logical volume identifier may correspond to a uniqueidentifier of the logical volume mapped via the first VIOS as a backingdevice for the client. At 506, the multipath component 122 receives asecond inquiry response that includes the logical volume identifier fromthe second VIOS. The logical volume identifier from the second VIOS maycorrespond to the unique identifier of the logical volume mapped via thesecond VIOS as a backing device for the client.

When the client performs device discovery (e.g. in order to discover andconnect to the virtual disk), the multipath component 122 can determinewhether the virtual disk is backed by the same logical volume (via themultiple VIOSs), based on the logical volume identifiers received fromthe inquiry responses. For example, if the logical volume identifiersare the same, the multipath component 122 may determine that the samelogical volume is accessible via the multiple VIOSs, and, at 508, createat least a first path and second path to the logical volume backedstorage device for the client.

In one embodiment, the multipath component 122 can also identify (forthe client) which paths are active/inactive, based on one or moreresponses to mode sense commands. For example, the multipath component122 can send a mode sense command to the first VIOS and the second VIOS.In response to the mode sense command, the first VIOS and second VIOSmay send responses indicating their respective access configurations (orpermissions) for the logical volume. For example, if the first VIOS isconfigured for read/write access to the logical volume, the first VIOSmay send a response that indicates the path via the first VIOS is anactive path. Similarly, if the second VIOS is configured for read onlyaccess to the logical volume, the second VIOS may send a response thatindicates the path via the second VIOS is an inactive path. Once thepath settings are determined, at block 512, the multipath component 122may use the active path to access (e.g., perform read/write I/O) thelogical volume backed storage device.

FIG. 6 is a flow chart illustrating a method 600 for switching one ofmultiple paths used to access a logical volume, according to oneembodiment. As shown, the method 600 begins at block 602 where theclient (e.g., LPAR 120) accesses a logical volume backed device from afirst VIOS (e.g., VIOS 128A) via a first path that is active (e.g., path230). At block 604, the multipath component 122 determines if the accessto the logical volume backed device is successful. That is, if a writeI/O was performed, the multipath component 122 determines if the writeI/O failed. If the access is successful, the client may continueaccessing the logical volume backed device via the first VIOS. On theother hand, if the access is not successful, the multipath component 122can switch the first path from an active state to a standby state. Inone embodiment, the multipath sends a command (e.g., mode selectcommand) to the first VIOS via the first path to make the first pathpassive (block 606) (i.e., switch the first path from an active state toa standby state). The mode selected command, for example, may change aconfiguration of the logical volume (or volume group) on the first VIOSto read only mode.

As noted above, in some cases, if the first VIOS is down, the multipathcomponent 122 may not receive a response to the mode select command(e.g., the hypervisor may reject the command). In such cases, themultipath component 122 may not have to make the first path inactivesince the first VIOS is not accessing the logical volume. On the otherhand, if the first VIOS is active, the multipath component 122 mayreceive a response indicating the first VIOS has changed the permissionof the volume group to read only.

At block 608, the multipath component 122 sends a command to the secondVIOS via a second path (to the logical volume backed device) to make thesecond path active (e.g., switch the second path from a standby state toan active state). The command sent to the second VIOS, for example, maychange a configuration (or permission) of the logical volume on thesecond VIOS to read/write mode. At block 610, the client may then accessthe logical volume backed device from the second VIOS via the secondpath. Advantageously, the techniques presented herein allow computingdevices to provide MPIO for logical volume backed virtual disks exportedfrom different VIOS, which may provide high availability for a logicalvolume backed virtual disk configuration.

FIG. 7 illustrates a computing system 700 configured to provide MPIO forlogical volume backed storage devices through redundant VIOSs on thecomputing system 700, according to one embodiment. As shown, thecomputing system 700 includes, without limitation, a central processingunit (CPU) 705, a network interface 715, a memory 720, and storage 760,each connected to a bus 717. The computing system 700 may also includean I/O device interface 710 connecting I/O devices 712 (e.g., keyboard,mouse, and display devices) to the computing system 700. Further, incontext of this disclosure, the computing elements shown in thecomputing system 700 may correspond to a physical computing system(e.g., a system in a data center) or may be a virtual computing instanceexecuting within a computing cloud.

The CPU 705 retrieves and executes programming instructions stored inthe memory 720 as well as stores and retrieves application data residingin the memory 720. The interconnect 717 is used to transmit programminginstructions and application data between CPU 705, I/O devices interface710, storage 760, network interface 715, and memory 720. Note CPU 705 isincluded to be representative of a single CPU, multiple CPUs, a singleCPU having multiple processing cores, and the like. Memory 720 isgenerally included to be representative of a random access memory. Thestorage 760 may be a disk drive storage device. Although shown as asingle unit, storage 760 may be a combination of fixed and/or removablestorage devices, such as fixed disc drives, removable memory cards, oroptical storage, network attached storage (NAS), or a storagearea-network (SAN). The storage 760 includes resource configurationinformation 762. Illustratively, the memory 720 includes a multipathcomponent 122, which is described in more detail above.

The descriptions of the various embodiments of the present disclosurehave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

In the following, reference is made to embodiments presented in thisdisclosure. However, the scope of the present disclosure is not limitedto specific described embodiments. Instead, any combination of thefollowing features and elements, whether related to differentembodiments or not, is contemplated to implement and practicecontemplated embodiments. Furthermore, although embodiments disclosedherein may achieve advantages over other possible solutions or over theprior art, whether or not a particular advantage is achieved by a givenembodiment is not limiting of the scope of the present disclosure. Thus,the following aspects, features, embodiments and advantages are merelyillustrative and are not considered elements or limitations of theappended claims except where explicitly recited in a claim(s). Likewise,reference to “the invention” shall not be construed as a generalizationof any inventive subject matter disclosed herein and shall not beconsidered to be an element or limitation of the appended claims exceptwhere explicitly recited in a claim(s).

Aspects of the present disclosure may take the form of an entirelyhardware embodiment, an entirely software embodiment (includingfirmware, resident software, microcode, etc.) or an embodiment combiningsoftware and hardware aspects that may all generally be referred toherein as a “circuit,” “module” or “system.”

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

Embodiments of the invention may be provided to end users through acloud computing infrastructure. Cloud computing generally refers to theprovision of scalable computing resources as a service over a network.More formally, cloud computing may be defined as a computing capabilitythat provides an abstraction between the computing resource and itsunderlying technical architecture (e.g., servers, storage, networks),enabling convenient, on-demand network access to a shared pool ofconfigurable computing resources that can be rapidly provisioned andreleased with minimal management effort or service provider interaction.Thus, cloud computing allows a user to access virtual computingresources (e.g., storage, data, applications, and even completevirtualized computing systems) in “the cloud,” without regard for theunderlying physical systems (or locations of those systems) used toprovide the computing resources.

Typically, cloud computing resources are provided to a user on apay-per-use basis, where users are charged only for the computingresources actually used (e.g. an amount of storage space consumed by auser or a number of virtualized systems instantiated by the user). Auser can access any of the resources that reside in the cloud at anytime, and from anywhere across the Internet. In context of the presentinvention, a user may access applications (e.g., multipath component122, management component 162, etc.) or related data available in thecloud. For example, the multipath component 122 could execute on acomputing system in the cloud, and map the logical volume on multipleVIOSs as a backing storage device for a client. Once mapped, themultipath component 122 can create multiple paths to the logical volumevia the multiple VIOSs. One of paths may be used to perform read/writeoperations and the other paths may be used as standby passive paths.Doing so allows a user to access this information from any computingsystem attached to a network connected to the cloud (e.g., theInternet).

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. A method, comprising: creating, from a physicalstorage device, a logical volume on a first virtual input/output server(VIOS); importing the logical volume to a second VIOS; and mapping thelogical volume on the first and second VIOSs as a backing storage devicefor at least one logical partition hosted on a computing system.
 2. Themethod of claim 1, further comprising: creating, from the at least onelogical partition, a first path to the logical volume via the first VIOSand a second path to the logical volume via the second VIOS; using thefirst path for accessing the logical volume; and using the second pathfor standby access to the logical volume.
 3. The method of claim 2,wherein creating the first and second paths comprise: sending a firstcommand to the first VIOS and the second VIOS to identify logicalstorage devices on the first and second VIOSs; after sending the firstcommand, receiving a response from the first VIOS that includes a firstlogical volume identifier for the logical volume and a response from thesecond VIOS that includes a second logical volume identifier for thelogical volume; and upon determining that the first logical volumeidentifier matches the second logical volume identifier, identifyingthat the logical volume via the first and second VIOSs is used as a samebacking storage device for the at least one logical partition on thecomputing system.
 4. The method of claim 3, further comprising: sendinga second command to the first VIOS and the second VIOS to determine aconfiguration of the first path and second path; determining that thefirst path is configured for at least one of read access and writeaccess to the logical volume based on a response to the second commandfrom the first VIOS; and determining that the second path is configuredfor read only access to the logical volume based on a response to thesecond command from the second VIOS.
 5. The method of claim 2, furthercomprising: upon determining that an operation to access the logicalvolume via the first path has failed: switching the first path from anactive state to a standby state; and switching the second path from astandby state to an active state; and performing read and writeoperations that access the logical volume from the second path.
 6. Themethod of claim 1, wherein the logical volume on the first VIOS and thelogical volume on the second VIOS are activated in a same access mode.7. The method of claim 1, wherein the physical storage device comprisesone or more physical disks, and wherein the logical volume comprises aplurality of the physical disks.
 8. A system, comprising: a processor;and a memory storing one or more instructions which, when executed bythe processor, perform an operation comprising: creating, from aphysical storage device, a logical volume on a first virtualinput/output server (VIOS); importing the logical volume to a secondVIOS; and mapping the logical volume on the first and second VIOSs as abacking storage device for at least one logical partition hosted on thesystem.
 9. The system of claim 8, the operation further comprising:creating, from the at least one logical partition, a first path to thelogical volume via the first VIOS and a second path to the logicalvolume via the second VIOS; using the first path for accessing thelogical volume; and using the second path for standby access to thelogical volume.
 10. The system of claim 9, wherein creating the firstand second paths comprise: sending a first command to the first VIOS andthe second VIOS to identify logical storage devices on the first andsecond VIOSs; after sending the first command, receiving a response fromthe first VIOS that includes a first logical volume identifier for thelogical volume and a response from the second VIOS that includes asecond logical volume identifier for the logical volume; and upondetermining that the first logical volume identifier matches the secondlogical volume identifier, identifying that the logical volume via thefirst and second VIOSs is used as a same backing storage device for theat least one logical partition on the system.
 11. The system of claim10, the operation further comprising: sending a second command to thefirst VIOS and the second VIOS to determine a configuration of the firstpath and second path; determining that the first path is configured forat least one of read access and write access to the logical volume basedon a response to the second command from the first VIOS; and determiningthat the second path is configured for read only access to the logicalvolume based on a response to the second command from the second VIOS.12. The system of claim 11, the operation further comprising: upondetermining that an operation to access the logical volume via the firstpath has failed: switching the first path from an active state to astandby state; and switching the second path from a standby state to anactive state; and performing read and write operations that access thelogical volume from the second path.
 13. The system of claim 8, whereinthe logical volume on the first VIOS and the logical volume on thesecond VIOS are activated in a same access mode.
 14. The system of claim8, wherein the physical storage device comprises one or more physicaldisks, and wherein the logical volume comprises a plurality of thephysical disks.
 15. A computer program product, comprising: acomputer-readable storage medium having computer-readable program codeembodied therewith, the computer-readable program code executable by oneor more computer processors to perform an operation comprising:creating, from a physical storage device, a logical volume on a firstvirtual input/output server (VIOS); importing the logical volume to asecond VIOS; and mapping the logical volume on the first and secondVIOSs as a backing storage device for at least one logical partitionhosted on a computing system.
 16. The computer program product of claim15, the operation further comprising: creating, from the at least onelogical partition, a first path to the logical volume via the first VIOSand a second path to the logical volume via the second VIOS; using thefirst path for accessing the logical volume; and using the second pathfor standby access to the logical volume.
 17. The computer programproduct of claim 16, wherein creating the first and second pathscomprise: sending a first command to the first VIOS and the second VIOSto identify logical storage devices on the first and second VIOSs; aftersending the first command, receiving a response from the first VIOS thatincludes a first logical volume identifier for the logical volume and aresponse from the second VIOS that includes a second logical volumeidentifier for the logical volume; and upon determining that the firstlogical volume identifier matches the second logical volume identifier,identifying that the logical volume via the first and second VIOSs isused as a same backing storage device for the at least one logicalpartition on the computing system.
 18. The computer program product ofclaim 17, the operation further comprising: sending a second command tothe first VIOS and the second VIOS to determine a configuration of thefirst path and second path; determining that the first path isconfigured for at least one of read access and write access to thelogical volume based on a response to the second command from the firstVIOS; and determining that the second path is configured for read onlyaccess to the logical volume based on a response to the second commandfrom the second VIOS.
 19. The computer program product of claim 16, theoperation further comprising: upon determining that an operation toaccess the logical volume via the first path has failed: switching thefirst path from an active state to a standby state; and switching thesecond path from a standby state to an active state; and performing readand write operations that access the logical volume from the secondpath.
 20. The computer program product of claim 15, wherein the physicalstorage device comprises one or more physical disks, and wherein thelogical volume comprises a plurality of the physical disks.